Closed vs open back cabs

Amps, Cabs, Speakers, etc
tunghaichuan
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Re: Closed vs open back cabs

Post by tunghaichuan » Tue Nov 17, 2020 7:01 pm

sclitheroe wrote:
Tue Nov 17, 2020 3:31 pm
tunghaichuan wrote:
Tue Nov 17, 2020 3:04 pm
sclitheroe wrote:
Mon Nov 16, 2020 6:58 pm
Would pulling the entire back off the cab be the answer? Or should a cab have some portion of the back covered?
Can you do that without damaging the cabinet?
Good question because the answer is...no. Just took a look. For some reason I thought there was an easy way to do it, but there certainly isn't. And I'd be reluctant to permanently modify the Greta cab, it's quite rare (not that I'm a collector really, I just don't see the sense in hacking it up)

I could always line out the Greta into the JC-120 or the Bassman for open back cab if I wanted, just need to look at what the output specs are before I do it :)
I agree with your assessment, you definitely don't want to hack up gear which is perfectly good as is. Especially when you may not even notice that much of a difference.

You might try something like this:

https://www.eminence.com/speakers/ext-c ... =XTC112_BT

It has removable panels so that you can experiment with both open and closed back configurations.

There are also 2x10 and 2x12 convertable cabs as well.

Mojotone has a convertable 1x12" cab as well:

https://www.mojotone.com/Cabinets_x/Cab ... -extension

tunghaichuan
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Re: Closed vs open back cabs

Post by tunghaichuan » Tue Nov 17, 2020 7:08 pm

laurie wrote:
Tue Nov 17, 2020 6:22 pm

Can I convert it to open back? Should some of the back be covered? There is a very long and detailed engineering answer to this that depends on the Thiele and Small parameters of the driver: https://en.wikipedia.org/wiki/Thiele/Small_parameters

The risk of getting it wrong is that the driver has excessive excursion and is damaged, or other electromechanical faults due to the impedance curve occur (e.g. burning out the driver). Or it simply sounds like crap. And unless you know the exact model number of the driver and the manufacturer has provided the Thiele and Small parameters, there is actually no way to use the math to figure things out.

However... With only 2W of power from the amp the risk of any speaker damage is pretty much zero. So I'd say just try various configurations until you find something that sounds good-to-your-ear.
I had my RSA Thiele cabs for at least 20 years before I actually knew what they were. I originally had them loaded with Celestions, not knowing any better. The cabs do sound much better with EV speakers, louder and punchier. The Celestions sounded flat and bland in comparison. But the Celestions I have are one of the most hated models.

IIRC, the Celestion website does not reommend using ported cabinets with their speakers. But, I used Celestions in my cabs for years with no problems. I had the cabs hooked up to an 80wpc MosValve amp, but never turned it up.

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bigtone23
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Re: Closed vs open back cabs

Post by bigtone23 » Sat Dec 05, 2020 7:36 am

I prefer closed back cabs. Open back cabs have to have a decent amount of internal volume to sound right and not boxy. The Blues Jr and Peavey Bravo are really congested sounding cabs to my ear. Too small for a 12" speaker. However, a Hot Rod Deluxe cab is big enough to sound open.
I usually play a 2x12" cab (Marshall 1936) away from home and it is a favorite of mine. My home cab is an old 1973 Orange 4x12" with Mesa MC90s wired for stereo or mono operation. I run a couple heads into it. I also have a Fender Bassman Ten with a closed back 4x10" cab. It thumps like a half stack since putting a quad of Celestion G12S-50 speakers in it.
I used to have a Mesa 1x12" Thiele cab loaded from the factory with a MC90. It sounded great and the speaker didn't fatigue. I'm sure Celestion doesn't recommend ported cabs now because there is a proliferation of extremely detuned guitar in the landscape. An 8 string has a low F#, that's a bass note of yore. The 20th century rarely saw a guitar go much lower than a low A.
I have a 1x12" Thiele type cab that is loaded and tuned for a Delta Pro 12A. It thumps rather nicely for bass, and adds a lot of low end as a guitar extension cab.
The benefit of guitar cabs is that you can be rather willy nilly with cutting holes in the back baffle to get various degrees of open back spread vs closed back punch and focus. A standard 6 string guitar tuned no lower than D standard isn't very hard on a single 10 or 12" speaker. Especially when not driven to it's extremes of power handling and excursion.
Can't go willy nilly with bass cabinets, though, you can easily destroy the speaker.

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laurie
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Re: Closed vs open back cabs

Post by laurie » Thu Dec 17, 2020 1:12 pm

Here's something I just came across - mentioned in a previous post, and easy to buy here in Canada.

https://qcomponents.ca/guitar-cabinets.html
Last edited by laurie on Fri Dec 18, 2020 7:46 pm, edited 1 time in total.

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Old_Iron
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Re: Closed vs open back cabs

Post by Old_Iron » Fri Dec 18, 2020 6:23 pm

This is something I never did, so it's just an info I read about.

If you want to record using an open back cabinet, you may use two microphones, one at the front and another at the back of the cabinet.

And the mic behind the cabinet must be out of phase of the one in front.

That would, supposedly, give you a sound of a bigger amplifier/cabinet.

Again, I never did it, so I don't know if it's true, but it seems right to me.

tunghaichuan
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Re: Closed vs open back cabs

Post by tunghaichuan » Fri Dec 18, 2020 10:08 pm

laurie wrote:
Thu Dec 17, 2020 1:12 pm
Here's something I just came across - mentioned in a previous post, and easy to buy here in Canada.

https://qcomponents.ca/guitar-cabinets.html
Those cabs are also available to buy in the US:

https://www.eminence.com/guitar-bass/ext-cab/

They look like nice cabs. I'd like to try a 2x12"

Luke Drifter
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Re: Closed vs open back cabs

Post by Luke Drifter » Wed Apr 27, 2022 9:53 am

closed back almost essential in large outdoor venues
Jerem, Jeremy on BAF and SBZ

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